The apparent capacity of lithium carbonate to prevent or attenuate manic and depressive recurrences has focused attention on the importance of long-term maintenance chemotherapy in recurrent affective illness. Unfortunately, there has been relatively little study of drugs other than lithium in this critical area of treatment. The proposed study will evaluate two alternatives to lithium therapy: a tricylic antidepressant and the combination of a tricyclic antidepressant and lithium. Patients will be classified according to the bipolar-unipolar dichotomy of depressive illness. Specifically, the primary purposes of the study are: 1) to compare the effectiveness of lithium carbonate, imipramine, placebo, and a combination of lithium and imipramine in the long-term maintenance treatment of unipolar recurrent affective illness; and 2) to compare the effectiveness of lithium, imipramine, and a combination of lithium and imipramine in the long-term maintenance treatment of bipolar recurrent affective illness. The study will involve the collaborative effort of four to six centers. Approximately 400 patients will be studied over a two-year period.